1. Field of the Invention
The present invention relates to an X-ray Talbot imaging apparatus which employs a Talbot interferometer or a Talbot-Lau interferometer.
2. Description of Related Art
An X-ray Talbot image capturing apparatus is known in which a Talbot interferometer or a Talbot-Lau interferometer, which captures and images the phase shift of X ray which occurs X ray is transmitted through a subject, and a radiation detector (Flat Panel Detector: FPD) are used (for example, refer to U.S. Pat. No. 5,812,629 and Junji Tanaka, et al. “Cadaveric and in vivo human joint imaging based on differential phase contrast by X-ray Talbot-Lau interferometry”, Z. Med. Phys. 23(2012)222-227). Hereinafter, such an X-ray image capturing apparatus employing a Talbot interferometer, a Talbot-Lau interferometer or the like will be referred to as an X-ray Talbot imaging apparatus.
An X-ray Talbot imaging apparatus includes a first grating (G1 grating) and a second grating (G2 grating) which are provided with slits at regular intervals. The second grating is disposed at one of the positions where self images of the first grating are formed at regular intervals on downstream side of the first grating by irradiating X ray to the first grating from an X ray radiation source. A Moire fringe is formed on the second grating by disposing the second grating such that the extending direction of the slits of the second grating is slightly inclined relative to the extending direction of the slits of the first grating. The X-ray Talbot imaging apparatus is configured to detect and capture the image overlapped with this Moire fringe (hereinafter referred to as a Moire image) by an X-ray detector disposed on downstream side of the second grating.
When a subject is disposed between the radiation source (or the radiation source grating) and the first grating or between the first grating and the second grating, a distortion is formed on the Moire fringe by the subject. Therefore, when a plurality of Moire images are captured by an X-ray Talbot imaging apparatus while the first grating and the second grating are relatively shifted (fringe scanning method), an image such as a differential phase image, an absorption image and a small-angle scattering image can be reconstructed and formed by the image analysis of the Moire image in an image processing.
An X-ray imaging apparatus is also known which is configured to control the irradiation time of X ray to a subject by an automatic exposure control (AEC) in order to obtain an appropriate image by irradiating X ray of appropriate irradiation amount to the subject in X-ray imaging of the subject (for example, refer to JP H08-241796A).